This invention relates to a propulsion system for contoured film embodied in a treatment surface for contoured films, said surface being provided with the propulsion system comprising one adjustable disk with a propulsion wheel and a second adjustable disk with an idler wheel. Each of the adjustable disks is provided with a steering mechanism. The films are most preferably represented by circularly contoured films. The invention also relates to a method for the propulsion and/or handling of any contoured film on a treatment surface comprising two adjustable disks, one disk being equipped with a propulsion wheel and the second disk with an idler wheel, whereby both disks provide a steering functionality in connection with the propulsion.
The state-of-the-art relating to film propulsion equipment is crowded and diverse. The art relating to the propulsion of contoured film is very limited in part due to the unusual problems to be resolved. Arcuately formed web of plastic film is used for the production of automobile windshields, having in particular a tinted band along the upper side. It is currently desirable to stretch the originally straight web, of for example polyvinyl butyral interlayer, into a curved web that fits along the upper side of the windshield. The so curved web is subsequently cut to produce the appropriate cut shaped blanks that will be used as interlayer between two sheets of glass for the manufacture of laminated windshields. After the stretching operation, the shaped web is normally manually moved over one or more cooling tables and is subsequently, also manually, cut to size. The propulsion of linear films on treatment surfaces by means of mechanical propulsion is well known and has been used for a long time. Non-linear films were, chiefly due to difficulties attached to controllable mechanical propulsion, mainly moved maually. Existing systems were notoriously deficient for moving, in a controlled manner, contoured films, particularly circularly shaped films.
U.S. Pat. No. 5,137,673 describes a process for forming cut shaped blanks of plasticized polyvinyl butyral of curved configuration matching the contour of the windshield of which the blank will be a component The film curvature is obtained by passing the film over frusto-conical rolls whereas one or more conical rolls will support the curved film along a forwardly curved arcuate path leading to the cutting station. U.S. Pat. No. 4,234,567 describes a set of conical pull rolls for moving circularly contoured film over a treatment surface. The apex of the conical rolls should coincide with the center of the film radius. It is also known that multiple driven wheels equally spaced across the width of the arcuately formed web can be used. The speed variations among the rolls then determine the radius of the path. JP-A-05329882 discloses the moving of film having a curved contour by using a movable die with curved wall into which the film is clamped JP-A-04292937 describes the moving of biaxially oriented film by means of a steam floating process. The prior art is not possessed of economically viable means for moving circularly contoured film along a circular path to thus secure, for treatment and/or handling purposes, a continously stable position in relation to selected reference points. Consequently, the like circularly curved films cannot be processed filly automatically but rather require, economically marginal, manual adjustments.
It is, therefore, a first object of the invention to generate a treatment surface which can be utilized beneficially for the propulsion and/or handling of contoured (non-linear/non-rectangular) films. Another object of the invention aims at providing a film treatment table which can serve for progressing/processing circularly contoured films in accordance with a selected pattern. Still another object of the invention relates at generating a film treatment surface equipped with a combined moving and steering mecanism. Yet another object of the invention aims at making available a method for continously propelling and/or handling a circularly contoured film along a circular path. The above and other objects of the invention can now be met with the aid of a treatment surface comprising, at least, two adjustable disks one of which is provided with steering and propulsion mechanisms whereas the second adjustable disk comprises a steering mechanism and an idler wheel. Further details of the inventive technology herein are described below.
The above and other objects are now accomplished by a treatment surface provided with a propulsion system for circularly contoured film along a circular path to thus secure, for treatment and/or handling purposes, a stable position of the film in relation to selected reference points comprising a handling surface having a first adjustable disk provided with a propulsion wheel and a steering mechanism and a second adjustable disk provided with an idler wheel and a steering mechanism